Trefoil factor family 2 (TFF2) is a unique member of the trefoil family expressed in gastric mucous neck cells (and lymphocytes). TFF2 is upregulated in gastric preneoplasia coincident with p53 mutations, and loss of p53 function is associated with dampening of immune responses to Helicobacter infection. Recent work from our laboratory has shown that TFF2-/- mice show a hyper-inflammatory phenotype, consistent with a putative role for TFF2 as an anti-inflammatory peptide. In response to long-term H. felis infection, TFF2-/- mice exhibit increased IFN-gamma levels and increased mucosal CD4+ T cells. Work from our laboratory has demonstrated that TFF2 transcription is regulated by the transcription factors p53 and KLF4 though an AP-1 site. In addition, we have made the unexpected observation that TFF2 is a natural ligand for the CXCR4 receptor, a G-protein coupled receptor and the primary receptor for SDF-1. TFF2 is a partial agonist for CXCR4, able to activate Ca++ signaling but in the presence of SDF-1, TFF2 partial inhibits SDF-1-dependent signaling and chemotaxis. Our overall hypothesis is that epithelial-derived TFF2 is regulated by p53 and inhibits SDF-1-dependent lymphocyte chemotaxis and survival, thus reducing inflammation. We propose to study the function and regulation of TFF2 through the following specific aims: (1). Investigate the role for p53 and KLF4 in the regulation of TFF2 gene expression. The role of p53 in repressing, and KLF4 in activating, TFF2 gene expression through an AP-1 site will be explored in gastric cancer cell lines and the roles of co-activators and co-repressors defined. (2). Confirm that TFF2 is a partial agonist and determine how TFF2 modulates SDF-1 signaling through CXCR4. We will investigate competition, the role of Galphai, downstream signaling pathways, and differences in receptor desensitization. (3). Show the importance of the TFF2-CXCR4 interaction in the modulation of T cell function. We will test the ability of TFF2 to regulate T cell migration and survival using both in vitro and in vivo model systems. (4) Clarify the importance of TFF2 in the gastric epithelium versus the hematopoietic compartment. Bone marrow chimerics, RAG2-/- reconstitution models, and crosses between TFF2-/- and p53 mutant mice will be employed to test the notion that TFF2 dampens gastric inflammation. Overall, these studies will define the role of TFF2 in immune modulation of the stomach. PUBLIC HEALTH RELEVANCE: The inflammatory response plays an important role in fending off infectious pathogens but over time can lead to organ failure or malignancy. Thus, chronic inflammation leads typically to the upregulation of a number of repair mechanisms, as well as the expression of peptides that can help to dampen or suppress the inflammatory response. We have studied trefoil factor family 2 (TFF2), a three-looped (clover leaf) shaped peptide that is upregulated in the chronically inflamed stomach, and have identified its primary receptor, which is known as CXCR4. This receptor is activated by a chemokine (known as SDF-1) that regulates lymphocyte function and thus we postulate that TFF2 functions by modulating responses by T cells to SDF-1. TFF2 is suppressed by the tumor suppressor gene p53, and we will also attempt to show that it is an important downstream target of this tumor suppressor through its activity in regulating the immune system.